Prop Shaft Drive Collet


As seen from the machining of part 162, the prop shaft, I did not machine any sort of drive bevel onto the shaft itself forward of the big front bearing. How to drive the prop? Key? Spline? Here's the simple answer. A split bronze collet is machined for a precise fit to the shaft, in my case a full 10mm diameter. The collet is split so that when the prop driver is seated, the collet grips the shaft with great force. An added benefit is that the action of seating the prop driver forces the collet against the inner race of the bearing, thus gripping the bearing tightly with no longitudinal play. The collet seen here has an ID of 10mm and a taper of 5 degrees. It measures 12mm in length.

  A blank of SAE 962 bronze is chucked, faced, and bored for a close sliding fit on the prop shaft. The bore must be made deep enough so that the threaded portion of the prop shaft may be inserted far enough to allow one to test the true 10mm portion.

Yes the lathe is running backwards, and a facing tool is used at the rear of the part!

Once the bore is satisfactory, the outer surface is taper turned, in my case, to 5 degrees.
Parted off, the collet is clamped in the mill vise, and a slitting saw of 0.023" width is used to slot the collet.
Installed on the shaft, with the bearing in place. Note how the installation will clamp the inner race of the ball bearing tightly.

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